Apedunculata discoidea Cuglianna, Cordeiro & Luque, 2009

Monteiro, Cassandra Moraes & Brasil-Sato, Marilia Carvalho, 2014, A new species of Anacanthoroides and redescription of Apedunculata discoidea (Monogenoidea) parasitizing Prochilodus argenteus (Actinopterygii) from the São Francisco River, Brazil, Zootaxa 3784 (3), pp. 259-266 : 262-265

Apedunculata discoidea Cuglianna, Cordeiro & Luque, 2009

( Figs 5–11 )

Hosts and localities. Prochilodus lineatus (Valenciennes) , from ponds in Pirassununga, (Paraná basin), State of São Paulo (type host and locality), and Prochilodus argenteus Spix & Agassiz , São Francisco River, near Três Marias, State of Minas Gerais (new host and locality), Brazil, all Prochilodontidae .

Site. Gills filament.

Studied specimens. Holotype CHIOC 36904; Paratypes CHIOC 36904 a–d, 36905, 36906 and 36907; Voucher specimens CHIOC 37102 (from P. lineatus ) and CHIOC 37910, 37911 a–b, 37912 a–b and 37913 (from P. argenteus ).

Redescription. [Dimensions from the type specimens (5 specimens) are followed by those collected in P. argenteus (11 specimens) between brackets, respectively.] Body divided into subspherical cephalic region, trunk and fused haptor forming a disk-shaped structure, 322 (293?338; n=5) [341 (327?398; n=8)] long, greatest width 233 (206?256; n=5) 215 [(193?245; n=8)] at the middle of the trunk. Cephalic lobes scarcely developed, three pairs of bilateral head organs; cephalic glands not observed. Four eyespots, members of the posterior pair slightly farther apart, larger than those of the anterior pair. Oral opening sub-terminal. Pharynx sub-oval to oval, 44 (43?46; n=5) [43 (41?48; n=8)] in diameter. Peduncle absent, haptor fused to trunk. Ventral anchors with similar, well-developed roots, elongated shaft, curved point not extending beyond the level of the tip of the superficial anchor root, 32 (31?36; n=5) [34 (31?39; n=8)] long, 26 (24?28; n=4) [25 (23?27; n=8)] wide. Ventral bar V-shaped, with central, elongated orifice, 17 (16?18; n=5) [17 (15?19; n=8)] long, 38 (35?41; n=5) [36 (34?39; n=7)] wide. Dorsal anchor with similar, well developed roots, short shaft and re-curved point not extending to the level of the tip of the superficial anchor root, 31 (28?34; n=5) [33 (29?37; n=8)] long, 26 (23?28; n=4) [24 (21?31; n=7)] wide. Dorsal bar elongated with two short, median and posterior projections 7 (6?11; n=2) [10 (9?14; n=6)] long, 40 (39?41; n=3) [44 (37?48; n=7)] wide. Hooks similar in shape, pairs 2 and 7, 29 (27?32; n=4) [29 (26?34; n=8)] long; other pairs 22 (20?23; n=12) [25 (19?27; n=21)] long; with recurved point, delicate shaft, elongated thumb and shank comprising 2 subunits; proximal subunit slightly expanded; filamentous extensions to the union of shank subunits. Testes 66 (60?72; n=5) [71 (67?83; n=8)] long; 63 (59?66; n=4) [61 (58?63; n=6)] wide, ovate; seminal vesicle 31 (28?39; n=5) [28 (26?43; n=5)] long, 33 (24?45; n=5) [30 (21?36; n=6)] wide; prostatic reservoir posterior to male copulatory complex, round, 31 (24?38; n=4) [34 (29?38; n=5)] long, 32 (22?38; n=4) [322 (293?338; n=5)] wide. Male copulatory organ comprised of a coil of 2 ½ to 3 counterclockwise rings arising from a small base; proximal ring diameter 28 (23?34; n=3) [322 (293?338; n=5)], 168 (148?198; n=3) [322 (293?338; n=5)] in total length; presence of two small, elongated projections connected to the base of the male copulatory organ, 8 (8?9; n=4) [7 (6?9; n=8)] long; accessory piece, not articulated to the male copulatory organ, comprised of two subunits, one elongated, serving as a guide for the male copulatory organ, 11 (9?14; n=4) [13 (9?16; n=7)] long, and the other Ushaped, connected to the first, 9 (9?11; n=4) [11 (9?13; n=6)] long; neither articulated to the male copulatory organ. Ovary elliptic to pyriform, 78 (73?85; n=4) [84 (79?91; n=5)] long, 59 (56?62; n=4) [62 (53?68; n=5)] wide. Vaginal pore sinistral; vaginal duct opening into central seminal receptacle. Vitelline follicles dense, lateral bands confluent with posterior gonads; transverse vitelline duct immediately anterior to gonads.

Remarks. In the original description, Apedunculata was characterized by the presence of: 1) a dextrolateral vagina that is slightly sclerotized, opening anteriorly at the level of the copulatory complex; 2) a copulatory organ coiled with two counterclockwise rings; 3) an accessory piece that is distal and not articulated; and 4) a body that is disk-shaped without a peduncle between the trunk and haptor. During the concomitant analyzes of the material deposited in CHIOC and specimens collected in P. argenteus it was possible to verify that in the original description Cuglianna et al. (2009) observed erroneously the direction of the dorsoventral axis of the speciemens of A. discoidea . As a result of this erroneous observation the internal structures were presented mirrored, an example is the vaginal opening that was described as dextrolateral but actually is sinistrolateral. The copulatory complex was described and it really is counterclockwise, but was represented as clockwise by Cuglianna et al. (2009). This makes necessary to amend the generic diagnosis of Apedunculata .

Apedunculata was originally compared to Demidospermus Suriano, 1983 and Gussevia Kohn & Paperna, 1964 . Comparing the diagnostic characters of Apedunculata with those of Demidospermus presented by Kritsky & Gutiérrez (1998), it was possible to observe the following: 1) the peduncle is reduced or absent in Apedunculata and elongated in Demidospermus , 2) the testis are dorsal to germarium in Apedundulata and post-germarial in Demidospermus , 3) the male copulatory organ of Demidospermus spp. is comprised of a single ring, but by more than one ring in Apedunculata , and 4) Demidospermus species are parasites in siluriform fish while Apedunculata parasitizes the gills of characiform fish ( Prochilodontidae ).

Comparing Apedunculata characters with those of Gussevia spp. presented by Kritsky et al. (1986), it is possible to distinguish them by the following: 1) MCO is counterclockwise in Apedunculata and clockwise in Gussevia ; 2) the haptorial peduncle is reduced or absent in Apedunculata and present in Gussevia ; 3) the presence of the anterior and posterior haptorial lobes in Gussevia spp. and the absence of a distinguishable haptor in Apedunculata , and 4) the use of cichlid fish (Perciformes) as hosts by Gussevia spp. and prochilodont fish ( Characiformes ) by Apedunculata .

Besides the genera initially compared to Apedunculata , after amending the generic diagnosis, it was found that Apedunculata shares some characters, such as a sinistral vagina and counterclockwise coiled male copulatory organ, with Ameloblastella Kritsky, Mendoza-Franco & Scholz, 2000 . However, according to Kritsky et al. (2000), Ameloblastella is also characterized by a fusiform body, absent eyes and an accessory piece articulated to the male copulatory organ, which are characters that are not shared with Apedunculata .

Apedunculata is a valid genus, and a parasite of prochilodontid gills characterized by the following combination of characters: 1) vaginal opening sinistrolateral slightly sclerotized, opening interiorly at the level of the copulatory complex, 2) coiled male copulatory organ with counterclockwise rings, 3) accessory piece distal and not articulated, and 4) disk-shaped body without peduncle.

The redescription of A. discoidea became necessary because some characters that were listed as diagnostic were not in agreement with those observed during the examination of type series and specimens collected in P. argenteus . In the description of A. discoidea , the authors mentioned the U-shaped ventral bar, but it is V-shaped with an elongated orifice in the central region that was not mentioned; however, this has been represented in the illustration of an entire specimen and observed in the type specimens and specimens from P. argenteus . The dorsal bar was characterized by the presence of median undulations, but in reality it is provided with two short projections located in the median region, oriented toward the posterior region of the body.

The record of A. discoidea in P. argenteus in the São Francisco watershed consists of a new host and locality for the species. It is likely that this species also occurs in this host or other Prochilodus species in other watersheds, but only future studies will elucidate the true distribution of this species.

Figures

FIGURES 5 – 11. Apedunculata discoidea from ‘ curimatã-pacú’, Prochilodus argenteus from the São Francisco River, Brazil, in ventral view (5) Whole mount (composite). (6) Ventral bar (7) Dorsal bar. (8) Ventral anchor. (9) Dorsal anchor. (10) Copulatory complex. (11) Hook. Scale = 70 µm (1) and 25 µm (6 – 11).